I have been every direction you comment about. Mallett with way too much horse power, but it never broke. But in honesty you are correct, I hated driving it. But the guy that bought it says his wife drives in all the time. Mine hated the car, but loved the look of it. I guess I am one of the few that actually bought a Mallett and made money on it. But was not a happier day than when it left to be honest.
I have two Redlines, one totally stock and nearly 80K on it. I bought it blown up because the guy who fixed it up left all the turbo ducts out of it. Put a new engine in it for 2K, bought the car for 2K and have another 1500 in it. Runs perfectly and is capable of playing with new Camaros and Super Snakes in the right circumstances, but not drag racing. I have a friend that drove a stock NA @Robotech
and gave the 400 and 500 HP Carmaro and G8's a lot of trouble on Mullholland a couple of years back.
I have a wildly modified Redline, which I am taking apart, but it plays quite well with the new Camaro SS's, not only in the twisties but in drags to. But not dependable, too many codes and no once seems to be able to fix it. Going back to the stock Turbo and Trifecta tune and just drive it. It has 35K on it and it is my favorite car of all time. I have had tons of hot rods, and classic cars with small blocks, both Ford and Chevy. Big Block Vettes and Mopar. The best street racer I ever had was a 1970 LT1 Z28 with tubohydro 400 behind it.
Overall, my yellow Redline/Opel wantabe is with out doubt the most fun car I have ever owned, and it has an Automatic in it.
We also have Sky NA, that is really fun to drive in the twisties. The other half has a Redline and NA. For cruises she like the Redline, and for daily driving she likes the NA. All look very close to new, and get continuous questions about what are they, who makes them and are they a new design.
So some of your comments are 180 degrees from what I have experienced with ours over the last 5 years.
Wish you luck with your project, but feel you have never truly played with a Redline that has been minimally tweaked. They really are quite impressive for something 12 years old.